batman-adv: add generic netlink family for batman-adv

debugfs is currently severely broken virtually everywhere in the kernel
where files are dynamically added and removed (see
http://lkml.iu.edu/hypermail/linux/kernel/1506.1/02196.html

 for some
details). In addition to that, debugfs is not namespace-aware.

Instead of adding new debugfs entries, the whole infrastructure should be
moved to netlink. This will fix the long standing problem of large buffers
for debug tables and hard to parse text files.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
[sven.eckelmann@open-mesh.com: Strip down patch to only add genl family,
add missing kerneldoc]
Signed-off-by: Sven Eckelmann <sven.eckelmann@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>